[Matplotlib-users] Why the V parameter in matplotlib.axes.Axes.contour must be increasing?

Xi Shen davidshen84 at gmail.com
Wed Aug 16 22:06:16 EDT 2017

Hi Jody,

I confirm that giving V = [0] to contour function in matplotlib gives me
the same image as using V = [0 0] in MATLAB.

Do you think it is a bug in matplotlib, or it is just a conscious design
decision? I do not have much knowledge of math behind this, so for me it is
just a restriction on parameter values.


On Thu, Aug 17, 2017 at 12:48 AM Jody Klymak <jklymak at uvic.ca> wrote:

> Hi David,
> I’ve definitely run into this, to my annoyance.
> Do you think you can open an issue on GitHub
> <https://github.com/matplotlib/matplotlib/issues>? If you don’t want to,
> I’m happy to do it.
> With respect to one contour at zero, its easier than Matlab:
> ax.contour(X, np.array([0.]))
> works for me…
> Cheers,
> On 16 Aug 2017, at 5:33, Xi Shen wrote:
> Hi,
> https://matplotlib.org/api/_as_gen/matplotlib.axes.Axes.contour.html says
> the contour function accept a vector parameter V which must be in
> increasing value. But the contour function in MATLAB does not have this
> restriction.
> I understand the underlining implementation of these two functions could
> be very different. I want to understand what is the purpose of this
> restriction, and if it possible to create a contour image the same as
> MATLAB does by using contour with V = [0 0]?
> Regards,
> David
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